Strong evidence supports the concept that in different cells of early cleavage stages of a variety of embryos, there exists a divergence in genetic activity due to unequal distribution of cytoplasmic regulatory factors, initially localized in eggs during oogenesis. Numerous examples demonstrate the importance of the resultant nucleo- cytoplasmic interaction in early embryogenesis for regional tissue differentiation during later development. My primary objectives are: 1) to understand the biochemical basis underlying mechanisms of macromolecular and particulate localizations in eggs, and 2) to develop a molecular assay to identify localized cytoplasmic regulatory molecules that elicit the appearance of specific gene products in certain regions of the embryo. Several hours after fertilization, a sulfated mucopolysaccharide (MPS) is localized in a defined region of the Fucus zygote, and following the first cell division, the localized MPS is partitioned into only the rhizoid cell. A specific glucanase also appears involved with the unique differentiated characteristics of the rhizoid cell. While Fucus will be used for the first objective, embryos of Vicia will be employed to characterize cytoplasmic components that may lead to the appearance of the protein legumin, which appears in localized regions of the young embryo. The specific aims of this proposal are: a) biochemically purify and characterize the MPS and glucanase which are localized in Fucus, and to determine their intracellular site(s) of synthesis, storage and transport by means of specific fluorescent-labeled antibodies and lectins; b) determine by flourescent microscopy and autoradiographic techniques, if the enzymatic sulfation of the MPS (which occurs just before its localization) is required for its transport, possibly via an endogenous electrical field; c) determine the role of the MPS-rich rhizoid cytoplasm on gene expression ofthe rhizoid nucleus; d) develop an in vitro assay system for cytoplasmic regulatory factors, using m-RNA for legumin synthesis; e) determine the site and time of m-RNA production for legumin synthesis, and if localized cytoplasmic components affect the control of these gene products.